Research On Method Of Operational Modal Parameter Identification Of Steel Plate Composite Beam Bridge

The modal parameters are the main parameters of the bridge's dynamic characteristics,which are of great significance to the assessment of the bridge's safety status,and the modal parameter identification based on the output data of the bridge's working state can more truly reflect the inherent dynamic characteristics and boundary conditions of the bridge,and does not affect the normal use of the bridge.Therefore,it has become the key research direction of modal parameter identification.In this paper,a 4 × 35 m steel plate composite beam bridge is taken as an example,only based on the out-put signal of the bridge in working state,the modal parameters of the bridge is identified by the method of random subspace and the combination of analytical mode decompositio n and random subspace.The effects of static mass and moving vehicle parameters on the recognition results is discussed.The main works are as follows:(1)The basic theory of random subspace method and analytical pattern decomposition theorem is introduced,and the extended discrete analytical pattern decomposition theory for discrete signals is derived.The method of selecting cut-off frequency by using self-regression power spectrum instead of Fourier spectrum is proposed.(2)The finite element model of the bridge is established,and the theoretical modal analysis is carried out.The acceleration signal of the bridge under the Gauss white noise and the earthquake excitation is obtained,based on the two methods,the identification result is obtained,then compared with the actual modal parameters of the bridge,the applicability of the two methods is verified.Finally,add different degrees of white noise interference to the out-put response,the accuracy of the two methods is compared.(3)The influence of the static mass on the calculated frequency of the bridge is analyzed.Based on vehicle-bridge coupled vibration theory,the acceleration signal of the bridge under the action of moving vehicles is obtained,based on the two methods,the identification result is obtained,and the influence of vehicle mass and vehicle speed on the loaded frequency of the bridge is analyzed.(4)The actual structure of steel plate composite beam bridge is taken as an engineering example.The acceleration signal of the bridge in the working state is collected on site,then the first two modal parameters of the actual bridge are obtained by using the two modal parameter identification methods proposed above.